1. Field of the Invention
The present invention relates to a printing apparatus and a printing method which print an image a print medium by conveying a print medium and determining a print timing for print data on the basis of positional information on the print medium being conveyed, the information being detected by a sensor configured to perform the detection.
2. Description of the Related Art
Many printing apparatuses and printing methods are known which involve an optical position detecting sensor for print media provided in a print medium conveying path to determine a print start timing for print data using as a print start reference a leading end detection information on the print medium obtained by the sensor so that printing of the print medium can be started at the determined print start timing.
Japanese Patent Laid-Open No. 6-135078 discloses a technique of determining whether a leading end or a trailing end of the print medium is used as a reference to set a print start position on the print medium so that if the front end of the print medium is used as the reference, the print start position on the print medium is placed at a print position after the front end has been detected, and so that if the rear end of the print medium is used as the reference, the print start position on the print medium is placed at the print position after the rear end has been detected.
However, with the conventional printing apparatus, printing is started at the print start position set on the basis of the leading end reference or trailing end reference of the print medium regardless of the size of the print medium in a conveying direction. Thus, if plural types of print media having different sizes in the print medium conveying direction are printed, then disadvantageously a plurality of image areas may be formed on the print medium in an unbalanced manner or the image may be partly missing.
For example, with the above-described printing apparatus, such a printing condition as shown in FIGS. 1 to 4 may occur. FIG. 1 is a schematic diagram of a monochromatic ink jet line printing apparatus equipped with a black ink ejecting line head (0105), showing that a post card (0101) as a print medium has been printed This printing apparatus performs one-pass printing by ejecting ink to a print medium (0101) passing under a line print head (0105). FIG. 1 shows that a recipient (an address and a name) (0102), a stamp positioning mark (0103), a sender (an address and a name) (0104) are appropriately printed on the postcard (0101). In contrast, if a postcard having a print medium length (the length in print medium conveying direction) different from that of the postcard shown in FIG. 1, such a printing condition as shown in FIGS. 2A and 2B may occur.
FIG. 2A shows that a postcard with a larger print medium length has been printed using the leading end as a reference. In this case, a margin at the trailing end (the bottom of the figure) of the postcard is excessively large as shown in FIG. 2A. FIG. 2B shows that a postcard with a larger print medium length has been printed using the trailing end as a reference. In this case, a margin at the trailing end (the top of the figure) of the postcard is excessively large as shown in FIG. 2B. FIG. 2C shows that a postcard with a smaller print medium length has been printed using the leading end as a reference. In this case, the sender name is partly missing. FIG. 2D shows that a postcard with a smaller print medium length has been printed using the trailing end as a reference. In this case, the name of the addressee is partly missing. Thus, printing by the conventional printing apparatus may result in unbalance between the print medium and the printed image.
FIG. 3 is a schematic diagram showing that an envelope (0301) pre-printed with an addressee (0302) has been printed using a color ink jet like printing apparatus equipped with a black ink ejecting line head (0306), a cyan ink ejecting line head (0307), a magenta ink ejecting line head (0308), and a yellow ink ejecting line head (0309). This printing apparatus performs one-pass printing by ejecting ink to the envelope (0301) passing under the line print head (0305).
FIG. 3 shows an example in which a postpaid postage mark (0303) and a sender (a company address, a company name, and a logo mark) (0304) are printed on the envelope (0301) by the above-described printing apparatus. In this example, the postpaid postage mark (0303) and the sender (0304) are appropriately printed by a printing operation using the leading end of the envelope as a reference. However, as shown in FIG. 4A, if an envelope with a larger print medium length is printed using the leading end thereof as a reference, the margin at the trailing end (the left of the figure) of the envelope may disadvantageously be excessively large, resulting in unbalance in the arrangement of the printed parts. Furthermore, as shown in FIG. 4B, if an envelope with a smaller print medium length is printed using the leading end thereof as a reference, the sender name may disadvantageously be partly missing.
On the other hand, Japanese Patent Laid-Open No. 9-168077 discloses a technique of printing an image using the leading end reference, and after the image formation, printing additional information (footer) using the trailing end reference. However, with the technique disclosed in Japanese Patent Laid-Open No. 9-168077, the image is always printed using the leading end reference, with the footer printed at a predetermined position located away from the area in which the image is printed. That is, the technique disclosed in Japanese Patent Laid-Open No. 9-168077 assumes that the print medium is large enough to allow both the image and footer to be printed thereon. Consequently, even with the technique disclosed in Japanese Patent Laid-Open No. 9-16807, a variation in the size of the print medium may still cause inconveniences such as the interference between the image, printed using the leading end reference, and the footer, missing of a part of the image, and the unbalanced arrangement of the image print parts.